What's this hole for?

[clanger9]

Quick question: this hole is on the right hand side, just next to the oil filler cap. What is it for?


It is shown as "042053" in the exploded diagram in the workshop manual, but I can't find that part in my parts list. It appears to go into the oil tank, so maybe some sort of breather?

[Ozmadman]

It's a botch!!! someone seemed to think the tank needed a breather for some reason so has hacked both outer casing and oil tank casing to fit a pipe to god knows where??? The oil tank has it's own very small breather hole right up inside in the RH crankcase that vents into the flywheel area anyway so there is no reason for someone to do this to the bike.. 042053 is the part number of the outer casing for an AJS model as it is a casing complete with the AJS badge but any casing will do.. Fortunately you can pick up an oil tank cheap on ebay. 1)It should look like this (NO HOLES!!) 2) this is what it looks like once you have the outer cover off and 3) here is a picture of where the breather vents inside the tank (the breather hole is that small hole toward the centre of the picture)

[clanger9]

Ah, that explains it. The bike is a former track bike, so there was probably a need for an external catch tank; hence the bodge!
I'll have a look inside to see if the internal breather has been blocked off...

[Ozmadman]

Ah, that explains it. The bike is a former track bike, so there was probably a need for an external catch tank; hence the bodge!
I'll have a look inside to see if the internal breather has been blocked off...

Should never be a need for any extra breather unless they have completely blocked off the crankcase breather on the other side. This is a breather rota on the crank which releases pressure once every revolution out of a small tube which exits the rear of the engine just in front of the gearbox sprocket.

[clanger9]

I think to get through scrutineering at track events you "had" to have a pipe from the engine breather to a catch tank.
Maybe this bodge was easier than trying to hook up to the real breather round the back of the engine...

Either way, thanks to your advice I now know it's not supposed to be there so I can block it off. I'll keep an eye out for an un-bodged cover on eBay.

[Ozmadman]

You will need an oil tank and outer cover. I have an outer cover, PM me and we can sort something out. If you are interested I can take a few pictures